Add docstring to check_availability_zone function
Add docstring to check_availability_zone function

Change-Id: Idc76dd50cb4808c10352f01329dab01c724c05b6

rahulunair/nova,mahak/nova,openstack/nova,klmitch/nova,klmitch/nova,openstack/nova,mahak/nova,rahulunair/nova,rahulunair/nova,openstack/nova,klmitch/nova,klmitch/nova,mahak/nova